Patients are undergoing more intravascular and minimally invasive procedures as alternatives to open surgical procedures. These less invasive procedures use a variety of catheters, and other devices which are placed in vascular, abdominal, pulmonary, urologic spaces with the goal of manipulating, cutting, and stabilizing structures at a distance from the operator. As every procedure has a certain failure rate, there will be by definition cases or instances where a component of the device separates and is difficult to retrieve or a material is placed or separates from a device and needs to be captured and removed.
In the setting of vascular procedures, a catheter segment, wire or balloon segment may become dislodged and must be recovered. In the setting of minimally invasive surgical procedures, a device component, suture clip, or staple, may be lodged in a small cavity or region where retrieval might be compromised or difficult with typical minimally invasive surgical devices. In the practice of biliary endoscopy and urology, stents and other catheters or other dislodged components may require subsequent retrieval.
Standard or direct explorations or excisions of the device elements or retained materials, can be overly invasive and traumatic, and inconsistent with the basic principles of minimizing direct trauma through minimally invasive procedures. Therefore, minimally invasive devices and techniques have been developed to retrieve dislodged foreign objects from the body.
Moreover certain pathologic materials, such as thrombi, emboli or stone excrescences, can be difficult to capture within delicate small spaces and require devices that can easily and efficiently capture or grab them for retrieval.
The use of retrieval devices for the removal of stones within the ureters, or bladder or within the biliary system are examples of the application of retrieval devices to remove pathologic materials that previously required open procedures, which often were associated with significant morbidities.
The development of stones within the ureters can result in renal insufficiency and recurrent infections. Removal of the stones can reverse obstructive phenomena, decrease pain, improve renal function and decrease recurrent infections. Biliary stones dislodged from the gallbladder can result in recurrent biliary obstruction, jaundice, pain and infection which can be alleviated by removal of the obstructing stone elements.
The development of a thrombus or dislodgment of an embolus within a vascular space results in downstream ischemia which can have profound physiologic consequences. If such an event occurs within the central nervous system, focal brain ischemia ensues resulting in the clinical manifestations of a stroke. The development of a thrombus or the dislodgment of an embolus into the peripheral vasculature can result in limb ischemia. Thrombi that develop in the coronary arteries result in myocardial infarctions.
Retrieval devices have been developed and applied to recovering vascular thrombi or emboli. The procedure of removing such a thrombosis is called an embolectomy and has been used by Interventional Radiologists and Vascular surgeons therapeutically. Removing these thrombi or emboli with minimally invasive procedures can be efficient and potentially less morbid then open direct procedures.
A number of retrieval devices have been designed and have entered the commercial marketplace. While a number of devices exist in the industry, there are generally four distinct type of devices that have gained more widespread popularity and use. In particular, the four types of devices can be referred to and identified as the (1) Gooseneck design snare; (2) Texan snare; (3) En Snare; and (4) the In Time retrieval device.
A review of some of the more common prior art devices reveals that the devices can be divided into three types of designs. The first type of design is a single snare or multiple looped snares that project from a catheter where the diameter of the snare loop or loops is controlled by advancing or retracting the catheter “over” the looped wire system or alternatively by advancing or retracting the wire system within a relatively stationary catheter system. The wire loop or loops can be manipulated or stabilized by the operator by a long wire which is connected to the loop or snare and extends distally to the proximal portion of a catheter system. Examples of this type of system include the Amplatz gooseneck system or the En Snare system marketed by InterV.
The second type of design is that of a mesh or basket configuration defined by multiple loops or struts that can be deployed through a catheter system. The basket or mesh system is attached to a wire which extends through a catheter system and is available to the operator at the proximal portion of the catheter. The geometry and therefore activation of a mesh system is controlled by the relative positions of the catheter meshed/wired structure. In some sense the relationship and control of the geometry of the wire loops is similar to a device of the first type in that a catheter initially constrains and keeps the wire mesh system from expanding as it is retained within the catheter lumen. Once the basket or mesh system is advanced through the catheter, it may expand to its fully deployed geometry.
After engaging a foreign body, the basket or mesh system can be retrieved by uniformly pulling back on the wire and catheter without changing the longitudinal relationship of the two components, hopefully with the foreign body engaged. Alternatively, the deployment catheter can be pushed back over the mesh system partially to change the geometry of the system and produce a capturing force along the surface of the foreign body. After such a maneuver, the longitudinal relationship of the activated mesh system and catheter are maintained and the system is removed hopefully with the foreign body.
A third type of device incorporates a multi-wired basket-like structure located at the end of a catheter system. The In Time retrieval system marketed by Boston Scientific is an example of this type of system. A wire mesh or multi-strutted system is attached to the tip of a microcatheter. The mesh or basket element appears not to be designed to be deployed from within the catheter system but is attached to its most distal end. The geometry of the mesh capturing system is controlled by a core wire that passes through the catheter system and attaches to the distal aspect of the mesh or basket system. The capturing element is “opened up” that is the spaces between the wires or struts are increased by decreasing the longitudinal length of the basket system by pulling back with the core wire. Once a foreign body is engaged within the capturing mesh wire system the spaces between the capturing struts can be decreased by elongating the wire system by advancing the core wire forward or distally. There is a possibility that the mesh system can be rotated by rotating the core wire. More specifically, the In Time product is made of a Nitinol braided microcatheter shaft, a radiopaque retrieval basket and a steerable Nitinol core wire.
There are a number of shortcomings in the design of the above-described conventional devices and their application in clinical practice which limit their effectiveness and/or simplicity.
The success of the retrieval procedure depends on the ability of the retrieval device to efficiently and reliably capture the foreign material. The initial steps of the procedure require that the retrieval device must come in contact with the foreign material in a way that allows the device to engage it or grab it. The efficiency of that step depends on the ability of the operator to control the position and contour of the wires/mesh in relation to the foreign material. Based on the design of the devices of the first type of retrieval devices, it may not be easy to change the contour or geometry of the snare loop by manipulating a wire at the proximal end of the catheter system. Rotating the catheter or the internal wire by rotating the wire at the proximal end of the catheter may not translate efficiently into controllable movements of the snare loop that will facilitate precise localization of the loop adjacent to the foreign material.
With respect to devices that are either of the second or third types in which the capturing element is a mesh or basket-like configuration, individual control of any particular wire loop within the mesh may be more problematic. The design concept in this type of system focuses on the fact that when deployed, the mesh system provides multiple “openings” through which a material potentially will be engaged. However, the fact that there is an increased number of notches or gaps in which a foreign material may enter only increases the probability that such an event will occur and does not guarantee it. The engagement is a relatively chance event and not necessarily driven by a precise alignment and control of a wire loop in the region of the foreign material. Also some of these designs depend on converting longitudinal translation of the core wire relative to the microcatheter into the precise localization of a wire or multiple wires which can be technically cumbersome.
The ability to engage a foreign material and capture it within the central portion of the basket structure can be compromised by the complicated woven structure of the basket wires which may impede transit and positioning of the foreign material within the basket's central portion.
The ability of the foreign material to remain securely engaged with the retrieval device depends not only on the force to which the material is exposed but the surface area of the grabbing or engaging element which is in contact with the foreign material.
The first type of device generally has one or a few snare loops that engage the foreign material. When the loop size is decreased, the foreign material is pushed against either the tip or distal side of the catheter. Although bringing the foreign material adjacent to the side of the catheter increases the surface area for contact, this type of orientation usually only applies to devices with a single capturing loop and the precision and geometry of engagement may not maximize surface area contact.
The surface area of engagement in devices that are either of the second or third types is limited to the surface area described by one or multiple relatively small diameter wires. If a foreign material is engaged between two wires, there will be minimal surface area in contact with the foreign material compromising the reliability of the capture. Of course, if the foreign material finds its way into multiple notches or gaps, the total contact surface area will increase and the engagement will be more secure. However the second possibility may only occur by chance since as above it is difficult to precisely direct such a mesh element to engage with a foreign material at multiple sites.
Although these types of devices can be useful in certain applications, other devices that maximize their ability to precisely, efficiently and securely capture foreign and pathologic objects may be more useful to the interventionalist.
The object of the present invention is to provide a device that overcomes these deficiencies and improves the retrieval procedure.
Other features and advantages of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.